Implement #pragma pack use in structure packing. The general approach
is to encode the state of the #pragma pack stack as an attribute when
the structure is declared.
- Extend PackedAttr to take an alignment (in bits), and reuse for
both __attribute__((packed)) (which takes no argument, instead
packing tightly (to "minimize the memory required") and for #pragma
pack (which allows specification of the maximum alignment in
bytes). __attribute__((packed)) is just encoded as Alignment=1.
This conflates two related but different mechanisms, but it didn't
seem worth another attribute.
- I have attempted to follow the MSVC semantics as opposed to the gcc
ones, since if I understand correctly #pragma pack originated with
MSVC. The semantics are generally equivalent except when the stack
is altered during the definition of a structure; its not clear if
anyone does this in practice. See testcase if curious.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@57623 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed